<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport"
        content="width=device-width, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0, viewport-fit=cover" />
    <title>rem</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        .my-box {
            margin-top: 20px;
            text-align: center;
        }

        .my-btn {
            display: inline-block;
            width: 20rem;
            height: 44px;
            line-height: 44px;
            background: #24A246;
            border-radius: 3px;
            font-size: 16px;
            color: #FFF;
            text-align: center;
        }
    </style>
</head>

<body>
    <div class="my-box">
        <div class="my-btn">按钮</div>
    </div>

    <script src="./rem.js"></script>
</body>

</html>